Contrasting behavior of the 52 and 73 fractional quantum hall effect in a tilted field

Using a tilted-field geometry, the effect of an in-plane magnetic field on the even denominator ν=52 fractional quantum Hall state is studied. The energy gap of the ν=52 state is found to collapse linearly with the in-plane magnetic field above ∼0.5T. In contrast, a strong enhancement of the gap is observed for the ν=73 state. The radically distinct tilted-field behavior between the two states is discussed in terms of Zeeman and magneto-orbital coupling within the context of the proposed Moore-Read Pfaffian wave function for the 52 fractional quantum Hall effect.